FR3124830A1 - Gas supply system for appliances using high and low pressure gas - Google Patents

Abstract

The present invention relates to a system for supplying (1) a high-pressure gas-consuming appliance (4) and a gas-consuming appliance at high pressure. low pressure (5) of a floating structure comprising a tank (8), the supply system (1) comprising a first supply circuit (2) of the device consuming high pressure gas (4) and a second supply circuit (3) of the low-pressure gas consuming appliance (5), characterized in that the supply system (1) comprises a return line (14) comprising a point of divergence (53) dividing the return line into a first section (51) and a second section (52), the supply system (1) comprising a first heat exchanger (6) and a second heat exchanger (7), the second section (52) bypassing the first heat exchanger (6). (figure 1)

Description

Gas supply system for appliances using high and low pressure gas

The present invention relates to the field of vessels for storing and/or transporting gas in the liquid state and more particularly relates to a gas supply system for consumer appliances included within such vessels.

During a journey made by a ship comprising a tank of gas in the liquid state intended to be consumed and/or to be delivered to a point of destination, said ship may be able to use at least part of said gas to the liquid state in order to supply at least one of its motors, via a gas supply system. This is the case for ships equipped with an ME-GI type propulsion engine. In order to supply this type of engine, the gas must be compressed at very high pressure by special compressors capable of compressing the gas up to 300 bars, but such compressors are expensive, generate substantial maintenance costs and induce vibrations. within the ship.

An alternative to installing these high-pressure compressors is to vaporize the gas in liquid form at 300 bars before it is sent to the propulsion engine. Since such a solution does not make it possible to eliminate the gas in vapor form (or BOG, which in English means "boil-off gas") which forms naturally within a tank containing at least partially the cargo, low-pressure compressors can be installed to power an auxiliary engine capable of consuming the gas in vapor form at low pressure. On the other hand, in such a configuration, if the gas in vapor form is present in too large a quantity, or more generally in a quantity greater than a consumption requirement of the auxiliary engine, the gas in vapor form not consumed by the auxiliary engine is then accumulated. in the form of pressure in the vessel within a certain limit, then eliminated by combustion or as a last resort by jettisoning in the atmosphere. Disposal in this way wastes fuel and has damaging consequences for the environment. Furthermore, the management of the gas in vapor form not consumed by the auxiliary engine can depend on the consumption of the gas initially in liquid form by the propulsion engine.

The present invention makes it possible to reduce or even eliminate the losses of gas in vapor form not consumed by the auxiliary engine and thus to improve the management of said gas in vapor form by proposing a gas supply system for at least one device high pressure gas consumer and at least one low pressure gas consumer device of a floating structure comprising at least one tank configured to contain the gas, the supply system comprising:

- at least one first gas supply circuit of the high-pressure gas-consuming device, comprising at least one pump configured to pump the gas sampled in the liquid state from the tank,

- at least one high pressure evaporator configured to evaporate the gas circulating in the first gas supply circuit,

- at least one second gas supply circuit of the low-pressure gas-consuming device, comprising at least one compressor configured to compress gas taken in the vapor state from the tank to a pressure compatible with the needs of the low-pressure gas consuming device,

characterized in that the supply system comprises a gas return line connected to the second supply circuit downstream of the compressor and comprising a point of divergence dividing the return line into a first section and a second section extending both from the point of divergence to the tank, the supply system comprising at least a first heat exchanger and a second heat exchanger, the first heat exchanger being configured to effect a heat exchange between the gas circulating at the vapor state in the first section of the return line and the gas in the liquid state circulating in the first supply circuit, the second section bypassing the first heat exchanger, the second heat exchanger being configured to operate a heat exchange between the gas flowing in the vapor state in the first section or in the second section of the return line and the gas in the liquid state flowing in the pr first supply circuit.

Thanks to such a supply system, the gas in the vapor state present in the tank and not used for the consumption of the low-pressure gas-consuming device can be condensed by circulating via the first section of the return line and is thus returned to the tank in the liquid state, instead of being eliminated. The loss of gas in the vapor state present in excess in the tank is then at least reduced.

In addition, when the flow rate of gas in the liquid state circulating in the first supply circuit is not sufficient to condense all of the gas in the vapor state circulating in the return line, the excess fraction of the latter can be directed to the second section of the return line to return directly to the tank. Such a situation can arise when the floating structure equipped with the supply system according to the invention does not require a large quantity of gas in the liquid state to be propelled, for example when the floating structure is moving at reduced speed.

It has been determined by the inventors that complete condensation of the gas in the vapor state circulating in the return line was only possible when the quantity of gas in the liquid state circulating in the first supply circuit is greater than or equal to six times the quantity of gas in the vapor state circulating in the return line. Such an example is applicable when the compressor compresses the gas in the vapor state to about 10 bars, but the ratio can change depending on the pressure delivered by the compressor. If this condition is met, the gas in the vapor state then circulates within the first section of the return line to be condensed. If the quantity of gas in the liquid state circulating in the first supply circuit is less than six times the quantity of gas in the vapor state circulating in the return line, then it is advantageous to circulate the gas at the vapor state at least partially within the second section of the return line, part of the gas in the vapor state then circulating in the first section in a quantity such that the condensation is complete.

The first gas supply circuit makes it possible to meet the fuel needs of the device consuming high-pressure gas. The latter can for example be the means of propulsion of the floating structure, for example an ME-GI engine. The first supply circuit extends from the tank to the high pressure gas consuming device. The pump is installed at the bottom of the tank and pumps the gas in liquid state so that it can circulate in the first supply circuit.

As the gas must be in the vapor state to be able to supply the high-pressure gas-consuming device, the high-pressure evaporator guarantees the evaporation of the gas before it is supplied to the high-pressure gas-consuming device. The high pressure evaporator is the seat of an exchange of calories between the gas in the liquid state circulating in the first supply circuit and a heat transfer fluid, for example glycol water, sea water or water vapour. The latter must be at a temperature high enough to create a change of state of the gas so that the latter changes to the vapor or supercritical state and supplies the high-pressure gas-consuming device.

Before the gas in a liquid state circulating in the first supply circuit is vaporized through the high pressure evaporator, the gas in a liquid state passes through the first heat exchanger, then the second heat exchanger . The temperature of said gas in the liquid state thus tends to increase before it passes through the high-pressure evaporator. Thus, the gas circulating in the first supply circuit can be in a two-phase state at the outlet of the second heat exchanger.

In general, the gas contained in the tank can pass naturally, or forced by the floating structure, into the vapor state. The gas within the tank passing to the vapor state must be evacuated so as not to create an overpressure within the tank.

Such a function is performed by the second gas supply circuit of the device consuming low-pressure gas. Such a second supply circuit extends from the tank to the low pressure gas consuming device. The latter can for example be an auxiliary motor such as an electric generator. The compressor arranged on the second supply circuit is responsible for sucking in the gas present in the top of the tank in order to be able to supply the low-pressure gas consumer device, but also to regulate the pressure within tank.

At the outlet of the compressor, the gas in the vapor state can supply the device consuming gas at low pressure, or circulate through the return line if the device consuming gas at low pressure does not require a supply of fuel . Since the return line is connected downstream of the compressor, the gas in the vapor state sucked in by the compressor can therefore circulate through it.

The vaporous gas flowing in the return line can flow into the first section or into the second section from the point of divergence. If the gas in the vapor state circulates in the first section, it first passes through the second heat exchanger, then the first heat exchanger, before returning to the tank. According to this configuration, thanks to the heat exchange taking place between the gas in the liquid state circulating in the first supply circuit and the gas in the vapor state circulating in the return line, the temperature of the gas at the vapor state decreases as it passes through the two heat exchangers, until said gas condenses and returns to the liquid state substantially at the outlet of the first heat exchanger. The condensed gas then circulates to the tank. If the gas in the vapor state circulates in the second section, it passes through the second heat exchanger and then returns directly to the vessel. According to this configuration, the temperature of the gas in the vapor state decreases due to the exchange of calories operated within the second heat exchanger, but is however not condensed. The gas thus returns to the tank in a vapor state, but is nevertheless cooled.

According to a characteristic of the invention, the high pressure evaporator and the second heat exchanger can form a single heat exchanger. The first heat exchanger is then separate and arranged upstream of this heat exchanger which brings together the second heat exchanger and the high pressure evaporator. Such an alternative can be advantageous, for example, in order to reduce the bulk of the power supply system. The single exchanger formed then comprises a first pass through which the gas in the liquid state of the first supply circuit circulates, a second pass through which the gas in the vapor state of the return line circulates and a third pass through which circulates the heat transfer fluid of the high pressure evaporator. Such a configuration of the power supply system constitutes a first embodiment of the power supply system according to the invention.

An embodiment in which the high pressure evaporator and the second heat exchanger are separate from each other constitutes a second embodiment of the supply system according to the invention.

According to a characteristic of the invention, the point of divergence can be arranged on the return line between the first heat exchanger and the second heat exchanger. In other words, the gas in the vapor state circulates within the first section or the second section after passing through the second heat exchanger. More particularly, it is a main section of the return line which crosses the second heat exchanger, said main section corresponding to the section of the return line upstream of the point of divergence with respect to a direction of circulation of the gas at the vapor state. Such a characteristic relates to the first embodiment and to the second embodiment of the power supply system as mentioned previously.

According to one characteristic of the invention, the point of divergence can be arranged on the return line, between the connection to the second supply circuit and the second heat exchanger, the first section and the second section passing through the second heat exchanger . This is a third embodiment of the supply system according to the invention, the high pressure evaporator and the second heat exchanger forming a single exchanger, just like for the first embodiment. According to this third embodiment, the point of divergence is arranged upstream of the second heat exchanger. The latter being configured to carry out a heat exchange in particular with the gas in the vapor state of the return line, each section among the first section and the second section passes through the second heat exchanger. Compared to what has been described previously, the single heat exchanger thus comprises a total of four passes, i.e. two passes for each of the sections of the return line in addition to the pass within which the heat transfer fluid circulates. high-pressure evaporator and the pass through which the gas in the liquid state of the first supply circuit circulates.

According to a characteristic of the invention, the second section of the return line comprises an end immersed in the liquid contained in the tank, the second section comprising an ejection member arranged at the level of the immersed end. The ejection device allows in particular to expand the gas in the vapor state circulating in the second section of the return line before the latter is dispersed in the tank. The expansion of the gas in the vapor state, associated with the fact that the submerged end is preferably arranged at the bottom of the tank, makes it possible to liquefy at least part of the gas in the vapor state when the latter returns to the tank, also causing a rise in temperature of the gas in liquid form present in the tank. The ejection member can for example be an ejector or a bubbling device.

According to a characteristic of the invention, the first supply circuit comprises an additional pump interposed between the first heat exchanger and the second heat exchanger. It is the additional pump which makes it possible to increase the pressure of the gas in the liquid state circulating in the first supply circuit, and this so that the latter has a compatible pressure for the supply of the consumer device of high pressure gas.

The positioning of the additional pump between the two heat exchangers is particularly advantageous. Indeed, setting up the additional pump upstream of the first heat exchanger leads to a rise in the pressure and temperature of the gas in the liquid state as soon as it passes through the first heat exchanger, which is detrimental to the condensation of the gas. in the vapor state circulating in the return line and also passing through the first heat exchanger. Furthermore, since the gas circulating in the first supply circuit can be in a two-phase state at the outlet of the second heat exchanger, placing the additional pump downstream of the second heat exchanger can be detrimental to the correct operation of the latter given that the additional pump only allows the pumping of a fluid in the liquid state. The optimal arrangement therefore consists of placing the additional pump between the two heat exchangers.

According to a feature of the invention, the first heat exchanger is configured to condense the gas flowing within the first section of the return line. The first heat exchanger is the exchanger through which the gas in the liquid state of the first supply circuit passes when said gas in the liquid state is at its lowest temperature. It is therefore the exchange of calories taking place within the first heat exchanger which will change the state of the gas circulating in the first section of the return line to make it pass from the vapor state to the liquid state. .

According to a characteristic of the invention, the second heat exchanger is configured to pre-cool the gas circulating within the return line. At the outlet of the first heat exchanger, the gas in the liquid state circulating in the first supply circuit is less cold than at the inlet of the first heat exchanger, a heat exchange having served to condense the gas at the vapor state of the return line. Subsequently, the gas in liquid state is compressed by the additional pump and then passes through the second heat exchanger. There is also an exchange of calories within the second heat exchanger, allowing the pre-cooling of the gas in the vapor state within the return line. Even if the flow of gas in the liquid state circulating in the first supply circuit is insufficient to operate a total condensation of the gas in the vapor state circulating in the return line, a cooling is however operated within the second exchanger heat.

According to one characteristic of the invention, the first section of the return line comprises an expansion member arranged downstream of the first heat exchanger. The expansion device provides expansion of the condensed gas flowing in the first section of the return line. The expansion device can also serve as a flow regulator circulating in the first section of the return line.

According to a feature of the invention, the second section of the return line comprises a flow control member. The flow control member can for example be a valve arranged downstream of the second heat exchanger in the case where the latter is itself arranged downstream of the point of divergence. The flow control device can also act as a pressure reducer. In the case where the second section of the return line is provided with an ejection member as described above, the flow control member is chosen so as to limit the expansion of the gas in the vapor state.

According to one characteristic of the invention, the supply system comprises an auxiliary supply line connected to the first supply circuit, upstream of the first heat exchanger, and extending as far as the second supply circuit, in downstream of the compressor, the supply system comprising a low pressure evaporator configured to evaporate the gas circulating in the auxiliary supply line. Such an auxiliary supply line is used when the low-pressure gas-consuming device needs to be supplied with gas in the vapor state, but the latter is not in sufficient quantity within the top of the tank. The auxiliary supply line thus makes it possible to divert part of the gas in the liquid state circulating in the first supply circuit. This part is then evaporated by the low pressure evaporator, according to an operation similar to that of the high pressure evaporator, that is to say by heat exchange with a heat transfer fluid such as glycol water, sea water or water vapour, for example. The low pressure evaporator thus induces an exchange of calories between the gas in the liquid state circulating in the auxiliary supply line and this heat transfer fluid.

Once in the vapor state, the gas continues to circulate within the auxiliary supply line and joins the second supply circuit in order to supply the low-pressure gas-consuming device.

If gas in the vapor state is present in sufficient quantity in the top of the tank, then the auxiliary supply line is not used and can for example be closed by a valve.

According to one characteristic of the invention, the pump is configured to raise a pressure of the gas in the liquid state to a value between 6 and 17 bars and the additional pump is configured to raise the pressure of the gas in the liquid state to a value between 30 and 400 bars. Such pressure ranges make it possible to raise the gas in the liquid state to a pressure compatible with each of the gas-consuming devices.

The additional pump makes it possible to raise the pressure of the gas in the liquid state to a value between 30 and 400 bars, in particular for use with ammonia and/or hydrogen, between 30 and 70 bars for use with liquefied petroleum gas, and preferably between 150 and 400 bar for use with ethane, ethylene or even with liquefied natural gas mainly consisting of methane.

According to one characteristic of the invention, the compressor is configured to raise a gas pressure to a value between 6 and 20 bars absolute. This pressure value ensures compatibility of the gas in the vapor state present in the top of the vessel and which is subsequently sucked into the second supply circuit with the device consuming gas at low pressure.

The invention also covers a floating structure for storing and/or transporting gas in the liquid state, comprising at least one tank of gas in the liquid state, at least one device consuming high-pressure gas, at least one low pressure gas consuming appliance and at least one gas supply system for these appliances.

The invention also covers a system for loading or unloading a liquid gas which combines at least one installation on land and at least one floating structure for storing and/or transporting liquid gas.

The invention finally covers a method for loading or unloading a liquid gas from a floating structure for storing and/or transporting gas in which pipes for loading and/or unloading gas in the liquid state arranged on an upper deck of the floating structure can be connected, by means of appropriate connectors, to a maritime or port terminal in order to transfer the gas in the liquid state from or to the tank.

Other characteristics and advantages of the invention will become apparent through the description which follows on the one hand, and several embodiments given by way of indication and not limiting with reference to the appended diagrammatic drawings on the other hand, on which :

represents a first embodiment of a gas supply system according to the invention,

represents a second embodiment of the power supply system,

represents a third embodiment of the power supply system,

is a cutaway schematic representation of a tank of a floating structure and a terminal for loading and/or unloading this tank.

The terms "upstream" and "downstream" used in the following description are used to express positions of elements within gas circuits in the liquid state or in the vapor state and refer to the direction of circulation of said gas. within said circuit.

Figures 1, 2 and 3 show a gas supply system 1 arranged on a floating structure. The supply system 1 makes it possible to circulate gas which can be in the liquid state, in the vapor state, in the two-phase state or in the supercritical state, and this from a storage tank 8 and / or transport, and up to a high-pressure gas-consuming device 4 and/or a low-pressure gas-consuming device 5, in order to supply the latter with fuel.

Said floating structure can for example be a ship capable of storing and/or transporting gas in the liquid state. The supply system 1 is in this case capable of using the gas in the liquid state that the floating structure stores and/or transports to supply the high-pressure gas-consuming device 4, which can for example be a motor propulsion, and the low-pressure gas consuming device 5, which can for example be an electric generator supplying the floating structure with electricity.

There represents a first embodiment of the supply system 1. In order to ensure the circulation of the gas contained in the tank 8 as far as the high-pressure gas-consuming device 4, the supply system 1 is provided with a first gas supply circuit 2. The first supply circuit 2 comprises a pump 9 disposed within the tank 8. The pump 9 makes it possible to pump the gas in the liquid state and to cause it to circulate in particular within the first supply circuit 2. By sucking the gas in the liquid state, the pump 9 also makes it possible to raise the pressure thereof to a value between 6 and 17 bars.

The gas in the liquid state, in a direction of circulation going from the tank 8 to the high-pressure gas-consuming device 4, passes through a first heat exchanger 6 and is pumped by an additional pump 10. Subsequently, the gas in the liquid state passes through a second heat exchanger 7 and a high pressure evaporator 11 forming a single heat exchanger 21. The details relating to the heat exchangers will be described subsequently.

The single heat exchanger 21, via the high pressure evaporator 11, makes it possible to modify the state of the gas circulating in the first supply circuit 2 in order to change it to the vapor or supercritical state. Such a state allows the gas to be compatible for supplying the high-pressure gas-consuming device 4. The evaporation of the gas in the liquid state can for example take place by heat exchange with a heat transfer fluid at a sufficiently high temperature. to evaporate the gas in the liquid state, here glycol water, sea water or water vapour.

The solution illustrated in makes it possible to design and manufacture the single heat exchanger 21 bringing together the second heat exchanger 7 and the high pressure evaporator 11, these two components being subjected to the same high pressure which dictates the technology used for the manufacture of this heat exchanger. common heat. Such a solution can also be justified by a lack of space which does not make it possible to set up the second heat exchanger 7 and the high pressure evaporator 11 separate from each other.

The increase in gas pressure is ensured by the additional pump 10 when the latter pumps the gas in the liquid state. The additional pump 10 makes it possible to raise the pressure of the gas in the liquid state to a value between 30 and 400 bars, in particular for use with ammonia and/or hydrogen, between 30 and 70 bars for a use with liquefied petroleum gas, and preferably between 150 and 400 bars for use with ethane, ethylene or even with liquefied natural gas consisting mainly of methane.

Thanks to the combination of the additional pump 10 and the single heat exchanger 21, the gas is at a pressure and in a state compatible for supplying the high-pressure consumer device 4. Such a configuration makes it possible to avoid the installation of high pressure compressors on the first supply circuit 2 which present cost constraints and generate strong vibrations.

Within the tank 8, part of the gas cargo can naturally pass into the vapor state and diffuse into a top of the tank 12. In order to avoid an overpressure within the tank 8, the gas at the vapor state contained in the top of tank 12 must be evacuated. However, the first supply circuit 2 is configured to use the gas in the liquid state to supply the high-pressure gas-consuming device 4.

The supply system 1 therefore comprises a second gas supply circuit 3, which uses the gas in the vapor state to supply the low-pressure gas-consuming device 5. The second supply circuit 3 extends therefore between the top of the tank 12 and the low-pressure gas consuming device 5. In order to suck the gas in the vapor state contained in the top of the tank 12, the second supply circuit 3 comprises a compressor 13. In addition to sucking in the gas in the vapor state, the compressor 13 also makes it possible to compress the gas in the vapor state circulating in the second supply circuit 3 to a pressure of between 6 and 20 bar absolute, and this in order to that the gas in the vapor state is at a pressure compatible with supplying the low-pressure gas-consuming device 5. The second supply circuit 3 thus makes it possible to supply the low-pressure gas-consuming device 5, and this while regulating the pressure within the tank 8 by sucking the gas in the vapor state present in the top of the tank 12.

The presence of gas in the vapor state in excessive quantity within the top of the tank 12 causes an overpressure within the tank 8. It is therefore necessary to evacuate the gas in the vapor state in order to lower the pressure within the vessel 8. The gas in the excess vapor state can then for example be eliminated by a burner 18 or, in a manner not shown, discharged into the atmosphere. However, the supply system 1 according to the invention comprises a return line 14 which extends from the second supply circuit 3 to the tank 8.

The return line 14 is connected to the second supply circuit 3 downstream of the compressor 13 with respect to a direction of circulation of the gas in the vapor state flowing in the second supply circuit 3. The return line 14 comprises in particular a main section 56 which begins at the level of the connection with the second supply circuit 3 and which extends to a point of divergence 53. At the level of the point of divergence 53, the return line 14 is divided into a first section 51 and a second section 52 both extending from the point of divergence 53 to the tank 8.

The point of divergence 53 is arranged downstream of the single heat exchanger 21. It is therefore the main section 56 of the return line 14 which crosses the single heat exchanger 21. As such, the single exchanger 21 therefore comprises a first pass 24 within which the gas in the liquid state of the first supply circuit 2 circulates, a second pass 28 within which the gas in the vapor state of the return line circulates 14 and a third pass 29 in which circulates the heat transfer fluid evaporating the gas in the liquid state circulating in the first pass 24.

At the outlet of the single heat exchanger 21, the gas in the vapor state circulates up to the point of divergence 53 and can subsequently circulate within the first section 51 or the second section 52. The first section 51 passes through the first heat exchanger 6 while the second section 52 extends as far as the tank 8 bypassing the first heat exchanger 6. In other words the gas in the vapor state can circulate within the first section 51 and be condensed thanks to the exchange of calories occurring at the level of the first heat exchanger 6, or can circulate within the second section 52 and return to the tank 8 in the gaseous state.

The choice of the section within which the gas in the vapor state circulates is in particular dependent on a flow rate of gas in the liquid state circulating in the first supply circuit 2, said flow rate having to be sufficient to completely condense the gas in the vapor state circulating in the return line 14. Thus, when the quantity of gas in the liquid state circulating in the first supply circuit is greater than or equal to six times the quantity of gas in the vapor state flowing in the return line, the gas in the vapor state can be directed towards the first section 51 so that the condensation thereof can be implemented.

If the quantity of gas in the liquid state circulating in the first supply circuit is less than six times the quantity of gas in the vapor state circulating in the return line, then a first fraction of the gas in the vapor state circulates within the first section 51 in a quantity such that the first fraction is entirely condensed within the first exchanger 6, while a second fraction of the gas in the vapor state, corresponding to the quantity of gas in the vapor state not circulating in the first section 51, circulates within the second section 52 in order to return directly within the tank 8. In the case where there is no or too little circulation of gas in the liquid state circulating in the first supply circuit 2, all of the gas in the vapor state then circulates in the second section 52 to return directly to the tank 8, in order to avoid a pressure drop resulting from crossing the first exchanger heat 6. In this condition, the The return of the gas to tank 8 takes place in the vapor state. Such a situation arises when the gas in the liquid state is little used to supply the device consuming high pressure gas 4.

In order to regulate the circulation within the return line 14, the first section 51 and the second section 52 respectively comprise an expansion device 15 and a flow control device 54. The expansion device 15 and the expansion device flow control can also ensure a function of expansion of the gas flowing in one or the other of the sections.

Advantageously, whether for the first section 51 or the second section 52, the gas which circulates there returns to the bottom of the tank 8 or at least to a zone where the gas is in liquid form. More particularly, the gas circulating in the vapor state in the second section 52 returns to the bottom of the vessel in the vapor state. The temperature and the density of the gas in the liquid state present in the tank 8 thus makes it possible to condense the gas in the vapor state leaving the second section 52. In order to facilitate this condensation of the gas in the vapor state, the second section 52 may comprise an ejection member 55 arranged at the level of one end of the second section 52 immersed in the tank 8. The ejection member 55 makes it possible to expand the gas in the vapor state circulating in the second section 52 in order to facilitate the condensation thereof within the tank 8. The ejection member 55 can for example be an ejector or a bubbling device. The return of the gas in the vapor state in the tank 8 via the second section 52 causes a rise in the temperature of the gas in the liquid state present in the tank 8.

It is at the inlet of the first heat exchanger 6 that the gas in the liquid state of the first supply circuit 2 has the lowest temperature. Therefore, it is therefore after having passed through the first heat exchanger 6 that the gas flowing in the first section 51 of the return line 14 is condensed. The gas in the return line 14 is therefore in the vapor state at the inlet of the first heat exchanger 6 and exits in the liquid state following the exchange of calories taking place within the first heat exchanger 6. The first heat exchanger 6 therefore acts as a condenser in the case where the gas in the vapor state circulates in the first section 51 of the return line 14.

The single heat exchanger 21 is located downstream of the first heat exchanger 6 according to the direction of circulation of the gas in the first supply circuit 2, and upstream of the first heat exchanger 6 according to the direction of circulation of the gas in the first section 51 of the return line 14. The single heat exchanger 21 therefore provides pre-cooling of the gas in the vapor state circulating in the return line 14 before it circulates in the first section 51 or in the second section 52. At the level of the first supply circuit 2, the gas in the liquid state at the inlet of the single heat exchanger 21 has previously passed through the first heat exchanger 6 and has been pumped by the additional pump 10, which therefore increased its temperature and pressure. It is thus possible that following the exchange of calories occurring at the level of the single heat exchanger 21, the gas circulating within the first supply circuit 2 leaves the single heat exchanger 21 in a liquid state. , steam, two-phase or supercritical. The temperature of the gas circulating in the return line 14 is therefore lowered after passing through the single heat exchanger 21, implementing the pre-cooling indicated above.

The additional pump 10 is advantageously arranged between the first heat exchanger 6 and the single heat exchanger 21. The presence of the additional pump 10 between the first heat exchanger 6 and the single heat exchanger 21 ensures that only gas in the liquid state circulates through the additional pump 10, and not gas in a two-phase state which risks damaging the latter.

Furthermore, the presence of the additional pump 10 downstream of the first heat exchanger 6 ensures the increase in pressure of the gas in the liquid state, and this without disturbing the exchange of calories occurring within the first heat exchanger 6 The condensation of the gas in the vapor state flowing in the first section 51 of the return line 14, if it takes place, is thus carried out in an optimal manner.

The supply system 1 also comprises an auxiliary supply line 16, extending from the first supply circuit 2, via a connection between the pump 9 and the first heat exchanger 6, to the second supply circuit 3, connecting to it between the compressor 13 and the low-pressure gas-consuming device 5. The auxiliary supply line 16 makes it possible to supply the low-pressure gas-consuming device 5 in the event of flow insufficient gas in the vapor state formed within the top of the vessel 12.

When the gas in the vapor state is not present in sufficient quantity in the head of the vessel 12, the gas in the liquid state pumped by the pump 9 can then circulate within this auxiliary supply line 16 in order to supplying the low-pressure gas-consuming device 5. To do this, the auxiliary supply line 16 passes through a low-pressure evaporator 17 so that the gas in the liquid state circulating in the auxiliary supply line 16 passes to the vapor state. The operation of the low pressure evaporator 17 can for example be identical to that of the high pressure evaporator 11, that is to say that the gas is evaporated by heat exchange with a heat transfer fluid at a sufficiently high temperature to evaporate gas in liquid state. At the outlet of the low-pressure evaporator 17, the gas in the vapor state circulates within the auxiliary supply line 16, then joins the second supply circuit 3 in order to supply the appliance consuming gas at low pressure 5.

It is understood from the above that the auxiliary supply line 16 is used only in the absence of gas in the vapor state in sufficient quantity within the vessel head 12. Thus, the auxiliary supply line 16 comprises a valve 19 controlling the flow of gas within the auxiliary supply line 16 when the use of the latter is not necessary.

There represents a second embodiment of the supply system 1 according to the invention. The second embodiment differs from the first embodiment in that the second heat exchanger 7 and the high pressure evaporator 11 are distinct from each other instead of forming the single heat exchanger illustrated in the previous figure. The rest of the supply system 1 is identical to what has been described above. We will therefore refer to the description of the about the structural and functional characteristics of the elements common to the two embodiments.

The first heat exchanger 6, the second heat exchanger 7 and the high pressure evaporator 11 are therefore heat exchangers separated from each other. Such a configuration makes it possible to design and manufacture each of the heat exchangers in a technology adapted to the pressure of the fluids traversing them. In the present case, the first heat exchanger 6 can be produced using a less expensive technology than that used for the manufacture of the second heat exchanger 7, because the pressure within the first heat exchanger 6 is significantly lower than that present within the second heat exchanger 7. The same applies to the high pressure evaporator 11.

The gas in the liquid state pumped by the pump therefore circulates in order through the first heat exchanger 6, then the second heat exchanger 7, and finally through the high pressure evaporator 11. At the level of the line return 14, the gas in the vapor state passes through the second heat exchanger 7, then optionally the first heat exchanger 6 in the event of circulation within the first section 51. According to the second embodiment, the point of divergence 53 is arranged downstream of the second heat exchanger 7.

There represents a third embodiment of the supply system 1. As for the first embodiment, the second heat exchanger 7 and the high pressure evaporator 11 are united to form the single heat exchanger 21. The third mode of realization differs on the other hand from the first embodiment by the fact that the point of divergence 53 is arranged upstream of the single heat exchanger 21. Thus, it is not the main section 56 which crosses the single heat exchanger. heat 21, but the first section 51 and the second section 52 which both pass through the single heat exchanger 21.

The single heat exchanger 21 therefore comprises here the first pass 24 within which the gas in the liquid state of the first supply circuit 2 circulates, the second pass 28 within which the gas in the liquid state possibly circulates. steam from the first section 51 of the return line 14, the third pass 29 within which circulates the heat transfer fluid evaporating the gas in the liquid state circulating in the first pass 24, and a fourth pass 32 within which circulates optionally the gas in the vapor state of the second section 52 of the return line 14. The third embodiment of the supply system 1 thus differs from the first embodiment in that the single heat exchanger 21 includes four passes instead of three.

At the outlet of the single heat exchanger 21, the first section 51 extends as far as the tank 8 crossing the first heat exchanger 6 while the second section 52 extends as far as the tank 8 bypassing the first heat exchanger 6.

There is a cutaway view of a floating structure 20 which shows the tank 8 which contains the gas in the liquid state and in the vapor state, this tank 8 being of generally prismatic shape mounted in a double hull 22 of the floating structure 20. The wall of the tank 8 comprises a primary sealing membrane intended to be in contact with the gas in the liquid state contained in the tank 8, a secondary sealing membrane arranged between the primary sealing membrane and the double hull 22 of the floating structure 20, and two thermally insulating barriers arranged respectively between the primary waterproofing membrane and the secondary waterproofing membrane and between the secondary waterproofing membrane and the double hull 22.

Lines 23 for loading and/or unloading gas in the liquid state arranged on the upper deck of the floating structure 20 can be connected, by means of appropriate connectors, to a maritime or port terminal to transfer the cargo of gas in the liquid state from or to the tank 8.

There also represents an example of a maritime or port terminal comprising loading and/or unloading equipment 25, an underwater pipeline 26 and an onshore and/or port installation 27. The onshore and/or port installation 27 can by example be arranged on the quay of a port, or according to another example be arranged on a concrete gravity platform. The onshore and/or port installation 27 comprises liquid state gas storage tanks 30 and connection pipes 31 connected by the subsea pipe 26 to the loading and/or unloading equipment 25.

To generate the pressure necessary for the transfer of the gas in the liquid state, pumps fitted to the onshore and/or port installation 27 and/or pumps fitted to the floating structure 20 are used.

Of course, the invention is not limited to the examples which have just been described and many adjustments can be made to these examples without departing from the scope of the invention.

The invention, as it has just been described, achieves the object it had set itself, and makes it possible to propose a gas supply system for appliances consuming gas at high or low pressure whose the high pressure is made using pumps and an evaporator, and comprising a means of condensing a gas in the vapor state before its return to the tank as well as an alternative return to the tank in case impossibility of condensing said gas in the vapor state. Variants not described here could be implemented without departing from the context of the invention, provided that, in accordance with the invention, they comprise a power supply system in accordance with the invention.

Claims (16)

System for supplying (1) gas to at least one high pressure gas consuming device (4) and at least one low pressure gas consuming device (5) of a floating structure (20) comprising at at least one tank (8) configured to contain the gas, the supply system (1) comprising:

• at least one first gas supply circuit (2) of the high-pressure gas consuming device (4), comprising at least one pump (9) configured to pump the gas sampled in the liquid state from the tank ( 8),
• at least one high pressure evaporator (11) configured to evaporate the gas flowing in the first gas supply circuit (2),
• at least one second gas supply circuit (3) of the low-pressure gas consuming device (5), comprising at least one compressor (13) configured to compress gas taken off in the vapor state from the tank ( 8) up to a pressure compatible with the needs of the low-pressure gas consuming appliance (5),

characterized in that the supply system (1) comprises a gas return line (14) connected to the second supply circuit (3) downstream of the compressor (13) and comprising a point of divergence (53) dividing the return line (14) into a first section (51) and a second section (52) both extending from the point of divergence (53) to the tank (8), the supply system (1) comprising at least a first heat exchanger (6) and a second heat exchanger (7), the first heat exchanger (6) being configured to operate a heat exchange between the gas circulating in the vapor state in the first section (51) of the return line (14) and the gas in the liquid state circulating in the first supply circuit (2), the second section (52) bypassing the first heat exchanger (6), the second exchanger heat exchanger (7) being configured to effect a heat exchange between the gas circulating in the vapor state in the first section (51) or in the second section (52) of the return line (14) and the gas in the liquid state circulating in the first supply circuit (2). Supply system (1) according to claim 1, in which the high pressure evaporator (11) and the second heat exchanger (7) form a single heat exchanger (21). Supply system (1) according to Claim 1 or 2, in which the point of divergence (53) is arranged on the return line (14) between the first heat exchanger (6) and the second heat exchanger (7 ). Supply system (1) according to Claim 1 or 2, in which the point of divergence (53) is arranged on the return line (14), between the connection to the second supply circuit (3) and the second exchanger heat exchanger (7), the first section (51) and the second section (52) passing through the second heat exchanger (7). A supply system (1) according to any preceding claim, wherein the second section (52) of the return line (14) includes an end submerged in the vessel (8), the second section (52) including an ejection member (55) arranged at the submerged end. Supply system (1) according to any one of the preceding claims, in which the first supply circuit (2) comprises an additional pump (10) interposed between the first heat exchanger (6) and the second heat exchanger (7). A supply system (1) according to any preceding claim, wherein the first heat exchanger (6) is configured to condense the gas flowing within the first section (51) of the return line (14) . Supply system (1) according to any one of the preceding claims, in which the second heat exchanger (7) is configured to pre-cool the gas circulating within the return line (14). Supply system (1) according to any one of the preceding claims, in which the first section (51) of the return line (14) comprises an expansion member (15) arranged downstream of the first heat exchanger (6 ). A supply system (1) according to any preceding claim, wherein the second section (52) of the return line (14) includes a flow control member (54). Supply system (1) according to any one of the preceding claims, comprising an auxiliary supply line (16) connected to the first supply circuit (2), upstream of the first heat exchanger (6), and s extending to the second supply circuit (3), downstream of the compressor (13), the supply system (1) comprising a low pressure evaporator (17) configured to evaporate the gas circulating in the supply line auxiliary (16). Supply system (1) according to any one of the preceding claims, in combination with claim 6, in which the pump (9) is configured to raise a pressure of the gas in the liquid state to a value comprised between 6 and 17 bars and the additional pump (10) is configured to raise the pressure of the gas in the liquid state to a value between 30 and 400 bars. Supply system (1) according to any one of the preceding claims, in which the compressor (13) is configured to raise a pressure of the gas to a value comprised between 6 and 20 bars absolute. Floating structure (20) for storing and/or transporting gas in the liquid state, comprising at least one tank (8) of gas in the liquid state, at least one device consuming high-pressure gas (4), at least one low-pressure gas-consuming appliance (5) and at least one gas supply system (1) for these appliances according to any one of the preceding claims. System for loading or unloading a liquid gas which combines at least one installation on land (27) and at least one floating structure (20) for storing and/or transporting liquid gas according to the preceding claim. A method of loading or unloading a liquid gas from a floating structure (20) for storing and/or transporting gas according to claim 14, in which pipes (23) for loading and/or unloading gas at the liquid state arranged on an upper deck of the floating structure (20) can be connected, by means of appropriate connectors, to a maritime or port terminal in order to transfer the gas in the liquid state from or to the tank (8 ).